Most important, be optimistic. While there are exceptions, most people cannot exist in society without creating a paper trail. Credit cards, mortgages, driver’s licenses — even voter registrations — are just a few of the countless ways a person lays a paper trail. What this means is that nearly every person is “findable.” You just have to know where and how to look.

You also must brace yourself, however, for a difficult challenge. Even in the age of the Internet — a tremendous boon to searchers — finding someone can be far more difficult than you expect. Success often requires dedication and patience. It also demands a willingness to.

What follows is some general advice I hope will help you in your search. It is only a starting point. The rest is up to you. Here are the four steps to success:

1. Be organized:Facts are essential. However, separating ordinary facts from the important facts can save you a lot of time.

As I gather facts about a person, I sort them into two categories: primary and secondary. A notebook can be a helpful way to divide and collect the facts as you find them. Draw a line down the center of a page and list the primary facts on the left-hand side, and secondary facts on the right. This not only helps you set priorities for searching; the mere process of writing things down sometimes stimulates new ideas. Any good investigator will write down and organize every good lead he or she collects.

Primary facts: Primary facts are those that can potentially lead you directly where you want to go (emphasis on the word directly). Think of them as stepping stones across a creek. You collect enough of them and you can get to the other side. Without them, you are stuck. Here are a few examples of primary facts:

Name (first, last and middle initial)
Date of birth (or at least approximate age)
Astrological sign
State
Social Security Number (SSN)
The state where a person was living - usually as a teenager - when they applied for their SSN.
Last known address (as long as it’s no more than 10 years old)

Armed with any or all of these, you are off to a good start. Of course, there are other types of primary facts. Any fact is a primary fact if it can potentially lead you to directly to the person for whom you are searching.

For example, let us say you happen to know that “Joe” graduated “ACME University.” This can be a primary fact because often schools will have alumni coordinators who might be able to forward a message from you to the person you are trying to reach. On the other hand, if the school has no such alumni coordinator, then you may have to classify this as a secondary fact. This brings up an important point: Some facts that seem at first to be secondary facts may later prove to be critical leads. Sometimes, even the reverse is true.

Occasionally, primary facts relate not to the person you wish to find, but to someone else. For example, I have no idea where my friend “Sylvia” might be, but I know if I find her brother “Ted,” he will know how to find her. (Searching for a male friend or relative can often be a good technique when searching for a woman, since many women change their last names upon marriage.)

Chances are good you will be missing at least some primary facts when you begin your search. Do not worry. As you dig, you will probably find more. You do not necessarily need all of them to be successful.

Secondary facts: Secondary facts are those that may prove helpful eventually, but they cannot help you immediately. There are countless examples, but here are a few to consider:

Anything relating to a person’s appearance the last time you saw them. Not only does a person’s appearance change over time, it is of no use at all in trying to locate them. As with any rule - there are sometimes exceptions. Once, I was searching for a man who actually belonged to a club called “The Bald Men’s Society!” You may obviously consider such a lead a primary fact! Still, a person’s physical description is usually not so helpful. It only helps confirm a person’s identity after you have already located them.

An address or telephone number more than 10 years old. While this can sometimes help, it is not usually the quickest way to go. Knowing where someone lived, say 30 years ago, may have little bearing on where this person lives today. Again, there can be exceptions. If a person prefers the Midwest by nature, this may be useful.

An adoptee’s given name at birth. Here again, a person’s “birth” name is likely not the one they ended up using.

These are just a few examples of secondary facts. They are good to note — you never know when something might prove useful — but focus on the primary facts first.

2. Think like an investigatorBear in mind two important principles.

The “paper trail”: Locating someone is all about finding the paper trail (even homeless people, prisoners and fugitives have one). Most of us create a paper with every new address form we fill out, every driver’s license we hold, every house we buy, every credit card we carry. There are other records, as well: parking tickets, lawsuits, professional licenses, criminal records, voter registrations, gun permits, etc.

If you are serious about finding someone, you need to approach the paper trail as an investigator would — and that means, consider everything! Because every case is different — and every person is different — it is impossible to suggest all the possibilities for locating someone’s paper trail. Be creative and brainstorm as many possibilities as you can. Did the person have any interests that could be a tool now for finding them? Clubs? School ties? Military service? Political interests? Career ambitions? Here are some other ideas: Is it likely this person is licensed? This list is longer than you might think. Doctors, dentists, taxi drivers, lawyers, nurses — even beauticians — are licensed in most states and the licenses are public record.

Is it possible this person has been searching for you? Particularly in adoption-related cases, some Web sites function as clearinghouses for birth parents and their children who wish to be found.

Do you know where the person you want to find attended high school or college? While most schools guard the privacy of their alumni, some may be willing to forward a letter for you to the person in question.

Is it possible the person is homeless? Homeless persons seldom move between cities. Contact the court clerk’s office in the county where you suspect the person might be. Often, you can search misdemeanor records that might give you clues. Homeless shelters in the area you are searching also may be willing to post notices/flyers.

The process of elimination: Successfully finding someone often involves eliminating the names of other people who are not the person you want to find. Let us say you are trying to find a person you went to college with — John Brown, hypothetically. It is obviously a common name and without more information, locating him might be extremely difficult. How might we narrow the search? Do you know his middle name? John Q. Brown, you say? Immediately you have narrowed the list - you can rule out all those with different middle names. Where there may have been thousands of John Browns out there, there may be only a couple hundred with the middle initial “Q.”

What about John’s birthday? You don’t know? OK, but you know approximately how old he would be, right? Let us assume he is 47-50. Now you have whittled the list of possible John Browns to an even smaller number.

Still, you need to push further. Let us consider the Social Security Number (SSN).

There is no more powerful tool for finding someone than the SSN (if you’re willing to pay to make use of it. Why? Because the Social Security Administration is not alone in using it. Any time you take out a credit card, or a loan, your lender requires your SSN on the application. This, coupled with your address and telephone number, form what is known as a “credit header.” While the header does not include any personal financial information, it contains all the information you need to find someone.

Of course, this information usually comes at a price. Assuming you have a SSN to work with in the first place, you will probably have to hire a licensed private investigator with access to a database of such information.

Perhaps you do not have John Q. Brown’s Social Security Number, but do you know where was he living when he obtained his SSN? (For most of us, this is the state where we lived as teenagers). The magic of SSNs is that they are coded - the first three digits indicate the state where you lived when your SSN was issued. You can find the full list of codes on the Social Security Administration Web site: http://www.ssa.gov/foia/stateweb.html).

Why is the SSN important? Because if we know that John Q. Brown likely spent his teenage years in New Jersey, we can surmise that his SSN starts with numbers between 135-158. Your list of hundreds of possible John Q. Browns just shrunk to dozens.

Finally, you must also consider all possible spelling variations of a person’s name, unless you are certain of the spelling (obviously a big advantage). “John” can also be “Jon” or even sometimes “Jack.” Or perhaps John goes by his middle name “Quentin.” Thinking of all the possibilities will not make your list any shorter, but it is the only way to make certain you will not miss a potential lead.

3. Turn to the WebThe Internet offers many free resources that can help you in your search. Below, I have assembled a list of links to help you get started. Because the list is long and constantly changing, it is not comprehensive. Nevertheless, here are a few suggestions:

4. Consider seeking helpIf you are serious about trying to locate someone who has proven difficult to find, you may wish to consider alternatives.

You can consider hiring a licensed private investigator. PIs usually have a wealth of experience, as well as some of the same investigative tools we use for “Dateline Lost & Found.” While these databases can be expensive and offer no guarantee of success, an experienced private investigator can often locate someone very quickly. If not, he or she may be able to suggest alternatives.

Be cautious about paying online search services that claim to be able to track down anyone for a small fee. Shop carefully, and be sure you know what you are paying for. Such services are seldom licensed or regulated.

Special situations
Adoption-related cases can be especially vexing. Because courts seal adoption records, it can be difficult even knowing where to begin. Even if you succeed in identifying a birth parent’s name, for example, you might find the leads are so old they are difficult to pursue. What is more, adoptive parents frequently change the name of the child they are adopting. This also clouds the “paper trail.”

Nevertheless, it is possible to locate someone connected with an adoption. If that is your situation, consider all the options listed on this Web site.

Also, in general, women are more difficult to locate than men are. This is because women often change their last names with marriage. A good strategy is to search for a woman via the men in her life. Does she have a brother? A father? An ex-husband Chances are, if you can find them, they can point you to her.

Stay the courseI like to keep people positive because I truly believe reconnecting with people you’ve cared about in life is worth doing. I also believe that doing so is almost always possible.

However, as you’ve certainly guessed if you’ve read through our “Dateline Lost & Found” Web site so far, searching for someone is rarely easy. The irony in this is that most people you set out to find never knew they were “lost” in the first place! I once found a man who couldn’t believe that the friend who’d been searching for him for 50 years had so much trouble!

Most people, however, simply aren’t trained in how to approach such a challenge. Having read this, I hope you will be a little better off in your search. Good luck!

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.